Thread by @BiIndia

A 'city-killer' asteroid got scarily close to Earth yesterday, and astronomers didn't know about it until it was just days away

businessinsider.in/a-city-killer-…

A 427-foot-wide asteroid whizzed within 45,000 miles of Earth yesterday.

While that may sound far away, 45,000 miles is what astronomers consider a close shave: It's less than 20% of the distance between Earth and the moon.

Although 2019 OK was wider than the #StatueofLiberty is tall, it's relatively small compared to the 6-mile-wide rock that hit modern-day Mexico and wiped out the dinosaurs 66 million years ago. @NASA NASA tracks about 90% of those types of big asteroids.

Research teams in Brazil and the United States didn't discover that 2019 OK was approaching until less than a week before it passed by.

Having as much advance notice of an impending collision as possible is imperative, because more lead-up time gives scientists a better chance of figuring out how to divert an asteroid from its current path.

One of those options is to launch an object into space to ram the incoming space rock head-on. Another involves what's called a #gravitytractor.

And to give such a notice, researchers at space agencies like @NASAEarth would have to make asteroid-detection work a bigger priority.